Magnet and movable contact support structure for a multiple contact electromagnetically actuated switch

ABSTRACT

THE CONSTRUCTIONAL DETAILS AND THE ARRANGEMENT OF THE COMPONENTS OF A MULTIPLE CONTACT ELECTROMAGNETICALLY ACTUATED SWITCH THAT HAS A CONTACT CARRYING PORTION OF A U-SHAPED MOVABLE CONTACT CARRIER MOVABLE IN AN EXTERNALLY EXPOSED SLOT IN A REAR WALL OF A BASE WHICH CARRIES THE STATIONARY CONTACTS. THE CONTACT CARRIER IS ACTUATED BY AN ELECTROMAGNET STRUCTURE THAT HAS THE STATIONARY MAGNET PART RESILIENTLY SUPPORTED ON A METAL HOUSING IN A MANNER SO THE STATIONARY MAGNET MOVES TOWARD THE ARMATURE TO MINIMIZE THE SHOCK AND THE BOUNCE BETWEEN THE CONTACTS OF THE SWITCH AND PERMIT THE METAL HOUSING TO ACT AS A HEAT SINK FOR THE HEAT ENERGY GENERATED WITHIN THE MAGNET WHEN THE ELECTROMAGNET IS ENERGIZED. THE COMPONENTS OF THE SWITCH ARE ARRANGED SO THAT THE SWITCH CAN BE READILY ASSEMBLED AND THE CONTACTS R THE ELECTROMAGNET CAN BE INDIVIDUALLY SERVICED WITH THE CONTACTS BEING READILY ACCESSIBLE IN EVENT THE MOVABLE CONTACTS ARE WELDED TO THE STATIONARY CONTACTS.

Jan. 5, 1971- M. Y. TURNBULL 3,553,515

MAGNET AND MOVABLE CONTACT SUPPORT STRUCTURE FOR A MULTIPLE CONTACT ELCTROMAGNETICALLY ACTUATED SWITCH Filed July 25, 1969 2 Sheets-Sheet 1 22 D24 #16 I72 48 BY MERLIN Y. TURNBULL Jan. 5, 1971 M. Y. TURNBULL MAGNET AND MOVABLE CONTACT SUPPORT STRUCTURE FOR A MULTIPLE CONTACT ELCTROMAGNETICALLY ACTUATED SWITCH Filed July 23, 1969 2 Sheets-Sheet 2 [NV/fN'fU/Q.

MERLIN Y. TURNBULL United States Patent 0 r ABSTRACT OF THE DISCLOSURE The constructional details and the arrangement of the components of a multiple contact electromagnetically actuated switch that has a contact carrying portion of a U-shaped movable contact carrier movable in an externally exposed slot in a rear wall of a base Which carries the stationary contacts. The contact carrier is actuated by an electromagnet structure that has the stationary magnet part resiliently supported on a metal housing in a manner so the stationary magnet moves toward the armature to minimize the shock and the bounce between the contacts of the switch and permit the metal housing to act as a heat sink for the heat energy generated within the magnet when the electromagnet is energized. The components of the switch are arranged so that the switch can be readily assembled and the contacts or the electromagnet can be individually serviced with the contacts being readily accessible in event the movable contacts are welded to the stationary contacts.

The present invention relates to electromagnetic type switching devices and more particularly to the constructional details and the arrangement of the components of a multiple contact electromagnetically operated switching device.

Electromagnetic switching devices of the type with which the present invention is concerned are commonly known as contactors and are furnished as devices of varying sizes having ratings in accordance with standards promulgated by the National Electrical Manufacturers Association, commonly known as NEMA. An example of a contactor construction which is particularly suited to control loads of 50 amperes or less, which corresponds to a NEMA Size 2 device is disclosed in US. Pat.

No. 3,354,415, which was granted on Nov. 21, 196-7 to t the inventors Joseph J. Gribble, Kenneth J. Marien and Harold E. Whiting.

, While the proportions of the device shown in the Gribble et al. patent may be increased to control greater than 50 amperes, economic and physical size limitation dictate that additional features should be incorporated therein if currents having a magnitude two or three times 50 amperes are to be controlled by the device. Thus the structure according to the present invention provides a higher degree of interphase isolation between adjacent switching contacts, a greater capability to extinguish arcs generated by the opening of the switching contacts, increased pressures between the switching contacts and a greater contact mass to enable the device to conduct the higher current values without overheating and without increasing the contact bounce characteristics of the device than was included in the structure disclosed in the Gribble et al. patent. Thus while the device according to the present invention incorporates the desirable features and advantages included in the device as disclosed in the Gribble et al. patent, it additionally includes a structure and an arrangement of components which can be economically 3,553,615 Patented Jan. 5, 1971 manufactured and provides capabilities not provided in the Grib-ble et a1. structure.

Accordingly, it is an object of the present invention to provide an electromagnetic switching device, commonly known as a contactor which, without a proportionate increase in cost or physical size, will be capable of switching larger currents without sacrifice of the features and advantages incorporated into the structure disclosed in the Gribble et al. patent.

An additional object is to provide a contactor that has a plurality of stacked components including an insulating base having spaced stationary contacts mounted on its front surface, an insulating barrier detachably mounted on the front surface of the base and cooperating with the base to define a plurality of spaced compartments that are substantially closed and electrically isolated from each other with each of said compartments having a pair of spaced stationary contacts therein, a metal housing secured on a front surface of the base 'with the metal housing providing a heat conducting sink for a magnet assembly that is positioned within an internal cavity of the housing, a cover removably secured on an open front side of the metal housing that includes a means for positioning the coil and a stationary magnet part within the cavity and a U-shaped contact carrier that has a portion movable in a slot in the rear wall of the base and a plurality of spaced projections extending into the compartments carrying movable contacts which are arranged to bridge the stationary contacts in the compartment when the magnet is energized.

A further object is to provide a contactor that has a plurality of stacked components including a metal mounting plate, an insulating base having a rear wall secured to the metal mounting plate, an insulating base having a rear wall secured to the mounting plate and spaced stationary contacts mounted on its front surface, an insulating barrier detachably mounted on the front surface of the base and cooperating with the base to define a plurality of spaced compartments that are substantially closed and electrically isolated from each other with each of said compartments having a pair of spaced stationary contacts therein, a metal housing secured on a front surface of the base with the metal housing providing heat conducting sink for a magnet assembly that is positioned within an internal cavity of the housing, a cover removably secured on an open front side of the metal housing that includes a means for positioning the coil and a stationary magnet part within the cavity, a U-shaped contact carrier that has a portion movable in a slot in the rear wall of the base and a plurality of spaced projections extending into the compartments carrying movable contacts which are arranged to bridge the stationary contacts in the compartment when the magnet is energized, and an insulating sheet positioned between the mounting plate and an insulating base providing spring seats for springs which urge the contact carrier to a position wherein the movable contacts are separated from the stationary contacts and a cover for a wire receiving groove in the plate.

Another object is to provide a contactor that has a plurality of stacked components including an insulating base having spaced stationary contacts mounted on its front surface an insulating barrier detachably mounted on the front surface of the base and cooperating with the base to define a plurality of spaced compartments that are substantialy closed and electrically isolated from each other with each of said compartments having a pair of spaced stationary contacts therein, a metal housing secured on a front surface of the base with the metal housing providing a heat conducting sink for a magnet assembly that is positioned within an internal cavity of the housing, a cover removably secured on an open front side of the metal housing that includes a means for positioning the coil and a stationary magnet part within the cavity, a U'shaped contact carrier that has a portion movable in a slot in the rear wall of the base and a plurality of spaced projections extending into the compartments carrying movable contacts which are arranged to bridge the stationary contacts in the compartment when the magnet is energized, and a bell crank lever interconnecting a movable magnet part of the magnet assembly with the movable, contact carrier.

Further objects and features of the invention will be readily apparent to those skilled in the art from the specification and appended drawings illustrating certain preferred embodiments in which:

v FIG. 1 is a perspective view of a switching assembly incorporating the features of the present invention.

FIG. 2 is a cross sectional view taken generally along line 2-2 in FIG. 1.

FIG. 3 is an exploded view showing in perspective certain components of the switching assembly in FIG. 1.

Referring to the drawing, and particularly to FIG. 1, there is shown an electromagnetic switch assembly having a plurality of components that are stacked one upon the other. The components of the assembly include a metal mounting plate 22, an insulating sheet-like member 24, an insulating base 26, an insulating barrier 28, a metal housing 30, and a cover 32.

r The metal mounting plate 22 is formed of a stamped metal part and provides a means to secure the switch assembly 20 to a vertical panel and the like, not shown. When the plate 22 is secured to a panel, an edge 34 becomes a bottom edge of the plate 22 and a surface 36 the front surface of the plate 22. The plate 22 has a pair of rearwardly extending indentations 38 along its bottom edge 34 providing a pair of spaced mounting feet having openings therein. The plate 22 also has an indentation 40 extending across its top edge which provides an elongated mounting foot having an opening therein. The mounting feet 38 and 40 with the openings therein are provided for the purpose of securing the plate 22 to a vertical panel. The plate 22 also includes an indentation 42 which extends from the bottom edge 34 rearwardly in the front surface 36 to the indentation 40. The indentation 42 is provided to permit passage of control wires 44 from the upper to the lower ends of the switch 20 in the space provided by the indentation 42 which acts as a wire trough for the wires 44. The control wires 44 are provided to be connected in circuit with the switching contacts of a device known as an overload relay in a manner well known to those skilled in the art.

The plate 22, most clearly shown in FIG. 3, is provided with four spaced threaded openings 46 which act as mounting holes which are used to secure the insulating sheet-like member 24 and base 26 together and to the plate 22. The sheet 24 is preferably formed as a molded insulating part having a relatively thin cross section having a flat rear surface engaging the front surface 36 to cover a central portion of the indentation 42 so as to act as a cover for the wire trough through which wires 44 extend. The sheet 24 has four holes aligned with the holes 46 and is provided with a pair of circular ribs 48 which are raised on the front surface of the sheet 24 on opposite sides of the indentation 42. The ribs 48 act as spring seats, as will be later described. The sheet 24 also is provided with portions 50 which are formed along the top and bottom edges of the sheet 24 in alignment with the indentation 42. The portions 50 act as scoops and aid in directing the wires 44 in the portion of the wire trough disposed between the sheet 24 and the plate 22.

The base 26 is formed of a molded insulating material having arc suppressing capabilities as are well known. The base has a rear surface 52 positioned on the insulating sheet 24 and the plate 22 in a secured position by suitable. screws which pass hro gh pe i g in the ba e '26 and the sheet 24 and are threadedly received in the mounting holes 46. Extending forwardly of a front surface 54 of the base 26 is a pair of spaced side walls 56 and pairs of posts 58 at the top and a pair of posts 60 at the bottom edge which effectively define an internal cavity 62 on the front surface 54. Extending between the posts 58 and 60 are two pairs of parallel ribs 64 and 66 which are spaced on the front surface 54 to effectively divide the cavity *62 into three compartments 68, 69 and 70, having equal widths. The ribs of the pairs of ribs 64 and 66 ar'e'spaced from each other to provide grooves 72 and 74, which are arranged to extend along the front surface 54 and into the posts 58 and 60 as shown. Extendinginto the material of the base 26 forwardly from the rear surface 52 and through the side walls 56 in a slot or passage '76. The slot 76 is centered on a center line equidistant between the topand bottom ends of the base 26 and, as illustrated in FIG. 2, is exposed to each of the compartments 68-70 by an opening 78 in the material forming the rear walls of the compartments 68-70 which extend on opposite sides of the centerline between the ribs 64 "and 66 as well as the side walls 56. The compartments 6870 extend to provide open exposed ends at the top and the bottom ends of the base 26. Embedded within the material of the base adjacent the open ends at the top and the bottom of each of the compartments 68-70 is a threaded insert 82 which is used to secure terminal and stationary contact assemblies in the compartments.

' Each of the compartments 68-70 has a Pair of stationary contact assemblies positioned so the contact assemblies of each pair are spaced equidistantly on opposite sides of the respective openings 78 and face in opposite directions. Each of the contact assemblies includes a terminal member 84, a contact member 86 and a conducting bar member 88. The bar member 88 has a threaded opening adjacent one of its ends and an unthreaded opening adjacent its other end. The terminal member 84 and the bar member 88 are secured adjacentan open end of the compartment by a screw 90. The screw 90 passes through an opening in the terminal member 84 and the unthreaded opening in the bar member 88 and is threaded into the insert 82. The contact member 86 in turn is secured to the bar member 88 by a screw 92 which passes through an opening in the contact member 86 and is threaded into the threaded opening in the bar member 88. As shown in FIG. 2, when the contact assemblies are secured at the opposite ends of the compartments 68-70, the terminal member 84 will have a wire connecting portion 94 extending external of the top and bottom wall of the base 26 and the contact portion 86 will have an inclined contact surface 96 positioned adjacent one of the openings 78.

The insulating barrier 28 is formed of a molded insulating material having arc suppressing capabilities as are well known. The barrier 28 has a front surface 98 and a rear surface 100 on a body portion 102 with ears 104 extending from the bottom and the top edges of the body portion 102 that are arranged to seat upon the forward ends of the'posts 58 and 60. The posts 58 and 60 each have'a threaded insert 61 molded therein and each of the ears 104 has an opening therein which permits the barrier 28 to be secured to the front surface of the base by screws 106 which pass through the openings in the ears 104 into the threaded inserts 61. Extending rearwardly' of the rear surface 100 are a pair of spaced ribs 108 and'110 which extend vertically between the top and the bottom edges of the barrier 28 and a pair of ribs 112 and 114 which extend horizontally along the top and i the bottom edges of the barrier 28 so as to intersect with 74 when the barrier 28 is secured to the base 26. Similarly, the ribs 112 and 114 are located and have their rear edges arranged so the ribs are positioned adjacent;

the cavity 62 side of the posts 58 and 60 with the rear edges of the ribs 112 and 114 juxtaposed to the heads of the screws 92 at the top and the bottom ends of the compartments 68 and 70. Thus the ribs 108, 110, 112 and 114 effectively cause the compartments 68-70' to be electrically isolated from each other and substantially causes the compartments 68-70 to be closed with the only openings into the closed compartments 68-70 being provided by the space between the rear edges of the ribs 112 and 114 and the front surface of the base 26.

The front surface of the barrier 28 has a configuration arranged to provide a socket 116 for a rear end of a magnet coil 117 of an electromagnet 119, a pair of guide surfaces 118 for an armature 121 of the electromagnet 119,

a groove 1'20 which receives a pivot pin 123 for a bell crank lever 125, spaces 122 and 124 for arm portions of the bell crank lever 125 and four suitably located bosses 126 each having a threaded insert embedded therein. The electromagnet 119 and the bell crank lever 125 have a construction as will be later described. Secured to the front surface of the barrier in the area defined by the socket 116 is a pad'128 of resilient elastromeric material which is engaged by the rear end of the coil 117.

The metal housing 30 preferably is formed as a die cast metal part with vertical walls arranged to extend forwardly in alignment with the side walls, the top wall and the bottom wall of the barrier 28 when the housing 30 is secured to the front surface 98 of the barrier 28. The vertical walls of the housing 30 and the front surface 98 of the barrier 28 define a cavity 130 having an open front end that is closed by the cover 32. Extending inwardly from the bottom wall 132 of the housing 30 is a portion 133 that is arranged to overlay the groove 120 so as to close the forward portion of the groove and maintain the pivot pin 123 in position within the groove 120. Also extending inwardly from the intersectionof the bottom wall 132 and the side walls 134 and 136 are suitably located ledges, not shown, having openings therein which are aligned with the inserts in bosses 126- adjacent the bottom edge of the carrier 28 so that a screw extending through the openings may be used to secure the bottom edge of the housing 30 to the front surface 98. Additionally extending inwardly from the top wall 138 of the housing into the cavity is a ledge,,not shown, having a pair of openings therein aligned with the inserts in the bosses 126 adjacent the top edge of the barrier 28 so that screws extending through the openings may be used to secure the top edge of the housing 30 to the front surface 98. Additionally extending inwardly at the intersection of the side walls 134 and 136 and the top wall 138 are ledges, not shown, which rest upon portions 140 and 142 on the surface 98 of the barrier 28. The ledges resting upon portions 140 and 142 provide a support for a pair of spring biased supports 144 for a stationary magnet part 127 of the. electromagnet 119 in a manner and for the purpose disclosed in an application for U.S. patent, Ser. No. 844,- 029, concurrently filed herewith which has been assigned by the inventors Harold E. Whiting and Merlin Y. Turnbull to the assignee of the present invention. The side walls 134 and 136 each have a portion 146 that projects outwardly to overhang the side walls ofthe barrier 28. Theportions 146 provide channel-like extensions for the cavity 130 with each of the channels having a ledge therein. The ledges, not shown, are provided with threaded openings to receive screws 148 which secure the cover 32 to the front edge of the housing 30.

The cover 32 is preferably formed of a molded material to have a configuration which matches the shape and length of the side walls 134 and 136, the bottom wall 132 and the top wall of the housing 38 so that when the cover is applied to the front edges of the walls of the housing 30, the cavity 130 will be closed. The cover is provided with an opening 150 which receives portions of the coil 117 and openings which are aligned with the channels formed by the portions 146 to permit screws 148 to be threaded into the threaded openings in the ledges in the channel provided by the portions 146 to secure the cover 32 to the housing 30. The cover 32 also has a pair of spring biased supports 156 secured thereon which are used to position the stationary magnet part 127 in a manner described in application 844,029, supra. Additionally, the cover is provided with an idented portion 158 which is formed as shown. The indented portion 158 provides access to the terminals 159 of the coil 117, permits observation of the operative condition of the electromagnet 119 through an opening 160 in the indented portion and attachment of auxiliary devices, such as a pilot light, in accordance with the disclosure of the Gribble et al. patent.

A movable contact carrier 16-2 is preferably formed as a U-shaped mold part to have a bight portion 164 and a pair of arms 166 extending from opposite ends of the bight portion 164. The bight portion is received in the slot 76 while the arms 166 extend externally of the side walls 56 and have ends received in the channels provided by portions 146 in the housing 30. Extending forwardly of the bight portion are a plurality of projections each of which extends through one of the openings 78-80 in the rear wall of the base 26 into one of the compartments 68-70 to provide a support 168 for a movable contact assembly indicated by the numeral 170 and fully disclosed in an application for U.S. patent, Ser. No. 844,151, which was filed by the inventor Merlin Y. Turnbull concurrently herewith. The movable contact carrier 162 is constantly urged in a forward direction to a position wherein the movable contacts 170 are separated from the contact portions 86 of the stationary contacts by a pair of springs 172. The springs 172 are of the compression type and each have one end seated in one of the spring seats defined by the circular ribs 48 and another end positioned in a recess, not shown, in the rear wall of the bight portion.

The electromagnet 119, which is more fully disclosed in an application for U.S. patent, Ser. No. 844,029, supra, includes the coil 117, the armature 121 and the stationary magnet part 127. The electromagnet 119 is positioned within the cavity with the stationary magnet part 127 resiliently positioned against the top wall 138 of the housing 30 so the housing acts as a heat sink for the heat generated by the electromagnet 119 when the coil 117 is energized. The coil 117 is positioned within the cavity by the socket 116 and is tightly held against the resilient pad 128 by portions of the cover 32 surrounding the opening when the cover 32 is secured to the housing 30. The armature 121 has its lower side operably connected to the bell crank lever 125 and its upper end extending into a central opening in the coil 117. The guide surfaces 118 serve as a guide for the armature 121. The bell crank lever 125 has a pair of arms operatively connected to the ends of the arms 166 in a manner disclosed in an application for U.S. patent, Ser. No. 844,100, which is concurrently filed herewith by the inventors Merlin Y. Turnbull and Harold E. Whiting.

The components of the switch assembly 20 may be assembled as follows. Initially the insulating sheet 24 is positioned on the mounting plate 22. as shown in FIG. 3. The movable contact carrier 162 is then positioned so the bight portion 164 is within the slot 76 and the arm portions 166 extend external of the side walls 56 of the base 26. The base 26 and the movable contact carrier 162 are assembled on the insulating sheet 24 and the mounting plate 22 by positioning the rear surface 52 adjacent on the sheet 24 with the springs 172 positioned between the insulating sheet 24 and bight portion 164 and tightening screws, notshown, which extend through suitable openings in the base 26 into the threaded openings 46. The stationary contact assemblies are then secured to the base 26 by tightening the screws 90 which pass through the unthreaded openings in the terminal member 84 and the bar member 88 into the threaded inserts 82 and tightening the screws 92 which extend through the unthreaded opening in the contact member 86 into the threaded opening in the bar member 88. The movable contacts 170 are then installed in the movable contact supports 168 in a manner disclosed in the US. application for patent, Ser. No. 844,- 151, supra. The barrier 28 is then installed on the front surface of the base by positioning the barrier 28 as previously described and tightening screws 106 extending through openings in the ears 104 into the inserts 6-1 in the posts 58 and 60.

The bell crank lever 125 is then positioned on the front surface 54 by positioning the pin 123 in the groove 120 and the arms of the bell crank, not shown, in the sockets at the ends of the arms 166 as disclosed in the application for US. patent, Ser. No. 844,029, supra. The housing 30 is then positioned on the front surface 98 of the barrier 28 so the portion 146 maintains the pin 123 in the groove 120 when suitable screws extending through openings in the ledges on the inner walls of the housing 30 are tightened into the inserts in the bosses 126. The electromagnet 119 including the coil 117, the stationary magnet part 127 and the armature 121 is installed in the cavity 130 in a manner disclosed in the application for US. patent, Ser. No. 844,029, supra. The installation of the cover 32 on the open side of the cavity 130 completes the assembly of the switching assembly when the screws 148 are tightened in suitable openings in the housing 30. It should be noted that the cover 32 when secured causes both the coil 117 and the stationary magnet part 127 to be properly positioned within the cavity 130.

The operation of the switching device is as follows. While the switch 20 will operate when mounted on a horizontal support, it is particularly suited to be mounted on a vertical panel, not shown, so that the armature 121 will be moved by the combined forces furnished by gravity and the springs 172 to a position whereat the pole faces of the armature 121 are separated from the pole faces of the stationary magnet part 127. The energization of the coil 117 through a suitable wire connected to terminals 159 causes a mutual magnetic attraction to be generated between the armature 121 and the stationary magnet part 127. The armature 121 is connected to the rotatable bell crank lever 125. The stationary magnet part 127 is resiliently maintained in engagement with the top wall 138 by the spring biased supports 144 and 156 that are respectively carried by the housing and the cover 32. It is well known that the magnet attraction between the armature 121 and the stationary magnet part 127 increases exponentially with the decrease in the distance between the pole faces of the armature 121 and the stationary magnet part 127 and the magnet attractionincreases to a maximum when the pole faces engage each other. The magnetic attraction between the armature 121 and the stationary magnet part 127 causes the armature 121 to move toward the stationary magnet part 127 and the bell crank lever 125 to rotate about the pivot pin 123. The rotating bell crank lever 125 causes the movable contact carrier 162 to move toward the plate 22 to a position wherein the movable contacts 170 engage the contact surfaces 96. The initial movement of the contact carrier 162 is opposed by the springs 172. The subsequent movement of the contact carrier 162, which occurs after the movable contacts 170 engage the contact surfaces 96, is opposed by the springs 172 as well as the springs associated with the movable contact structure 170. Thus the resistance to the movement of the armature 121 toward the magnet part 127 progressively increases as the springs 172 are compressed and markedly increases as the force required to compress the springs associated with the movable contacts is added to the force required to compress the springs 172. The magnetpart 127 is exclusively supported in the cavity 130 by the two pairs of spring biased supports 144 and 156 to have its base tightly pressed against the top wall 138 when the springs biasing the movable contacts and the springs 172 are fully compressed. Thus the heat generated within the electromagnet 119 when the coil 117 is energized will be readily transmitted to the metal housing 30 so the metal housing may serve as a heat sink and dissipate the heat energy generated within the electromagnet 119. However, the springs biasing the supports 144 and 156 are selected to provide a force which will permit the magnet part 127 to move in the direction of the armature 121 in response to the mutual flux between the armature 121 and the magnet part 127 just prior to the engagement between the magnet part 127 and the armature 121. Thus at the instant of impact, the armature 121 and the magnet part 127 will be moving in opposite directions with the magnet part 127 reversing its direction of movement and moving with the armature 121 after the impact has occurred between the armature 121 and the magnet part 127. While the causes therefor are not completely understood, it has been found that resiliently supporting rather than rigidly supporting the magnet part 127 on the housing 30 reduces the noise generated and the shock imparted to the housing 30 which accompanies the impact between the armature 121 and the magnet part 127. Further it has been found that the resilient support for the magnet part 127 reduces the shock imparted to the housing 30 when the electromagnet 119 is deenergized and the armature 121 is returned to its dropped-out position by the combined force provided by gravity and the springs 172 as well as the springs of the movable contact structure.

Further as disclosed in the Gribble et a1. Pat. No. 3,354,415, supra, and in patent application Ser. No. 844,151, supra, the movable contact 170 and its supporting structure provides an arrangement which will considerably reduce the bounce which accompanies the engagement between the movable contacts 170 and the stationary contact members 86. The switch 20 is arranged so either the electromagnet 119 structure or the contact structure can be serviced independently without disturbing any wire connections to the wire connecting portions 94. When the electromagnet 119 is to be inspected or serviced, ready access may be had thereto by merely removing srews 148 and the cover 32 so that the components of the electromagnet are fully accessible for inspection and replacement in the cavity 130. When the contact structures are to be inspected or replaced, all that is required is to remove the four screws 106 so that the barrier 28, the housing 30 and cover 32, including the electromagnet 119, may be removed from the base 26 with the movable contact carrier 162 remaining assembled with the base in a manner described in patent application Ser. No. 844,029, supra, so that even if the movable contacts 170 are welded to the contact surfaces 96, access may be had thereto for service purposes.

While certain preferred embodiments of the invention have been specifically discosed, it is understood that the invention is not limited thereto, as many variations will be readily apparent to those skilled in the art and the spaced compartments that are substantiallyclosed and electrically isolated from each other, said housing being secured on a front surface of the barrier and providing a heat conducting sink for a magnet assembly within an internal cavity in the metal housing, said cover secured on an open front side of the housing and providing a means for positioning a magnet coil of the magnet assembly within the housing, and a U-shaped movable contact carrier having a pair of arm portions extending adjacent the outer surfaces of a pair of opposite side walls of the base, a bight portion'extending in a slot in a rear wall of the base and a plurality of spaced projections on the bight portion with each of said projections extending through an opening in the rear wall into one of the compartments and providing a support for a contact that is movable in the compartment.

2. The switch assembly as recited in claim 1 including a metal mounting plate having a wire trough formed therein, and an insulating sheet-like member positioned between the rear surface of the base and the mounting plate providing a cover for a portion of the wire trough when the insulating sheet and base are assembled on the metal plate.

3. The switch assembly as recited in claim 2 including a pair of spring seats on the insulating member aligned with the slot in the base and a pair of springs each having an end seated in one of the spring seats and an end engaging the bight portion for urging the U-shaped carrier toward the front surface of the base.

4. The switch assembly as recited in claim 1 wherein the magnet assembly includes a stationary magnet part, a movable magnet part, and the coil and a bell crank lever interconnecting the movable magnet part and the arm portions and a pivot for the bell crank provided by portions of the barrier and the metal housing.

5. The switch assembly as recited in claim 1 including a pair of stationary contacts in each of the compartments with the pair of stationary contacts in each compartment mounted on equidistantly opposite sides of a center line through the slot in the base to provide contact surfaces that are engageable by contact surfaces on the movable contact.

6. The switch assembly as recited in claim 5 wherein the cover, the housing and the barrier are secured together to form a unit which can be removed from the insulating base as a unit to provide access to the compartments within the base.

7. The switch assembly as recited in claim 1 wherein the cover is independently removable from the housing to provide access to the magnet assembly within the housing while the base, the barrier and the housing are secured to each other.

8. The switch assembly as recited in claim 1 wherein the magnet assembly includes the magnet coil, and a magnet pole piece and a magnet armature and means for mounting the pole piece and armature within the housing so the pole piece and armature are each movable in the housing while the coil is immovably positioned in the housing by portions of the barrier and the cover.

9. The switch assembly as recited in claim 1 wherein a bell crank lever interconnects the armature and the movable contact carrier and portions of the bell crank lever act as a guide means for the contact carrier.

10. The switch assembly as recited in claim 5 wherein the bight portion of the contact carrier is movable in a plane extending through the center line and is guided for movement by portions of the base on opposite sides of the slot.

References Cited UNITED STATES PATENTS 3,354,415 11/1967 Gribble 335-132 HAROLD BROOME, Primary Examiner US. Cl. X.R. 

